Nailing machines comprised of a plurality of reciprocating nailing heads disposed above an anvil have been in use for some time for nailing deck boards to stringer beams to form either single or double deck pallets. However, the conveying mechanisms utilized with such machines have been unduly cumbersome and inefficient. Traditionally, special jigs have been utilized to hold stringer beams and deck boards in proper position for nailing, and conveyors have been provided to engage the jigs and pull them through the nailing machines as spaced stringer beams are successively nailed to deck boards. The manual loading of stringer beams and deck boards into such jigs is a time consuming, inefficient process. See, for example, U.S. Pat. No. 3,557,439 and the description of prior art are set forth therein. The pallet assembling system of this patent requires two nailing machines with a first deck being nailed in place to stringer beams in a first machine and a second machine being utilized to nail a second set of deck boards in place after the half pallet is turned over.
U.S. Pat. Nos. 3,591,067 and 3,552,624 disclose particular jig assemblies for supporting the stringers and deck boards of a pallet in position for nailing in a nailing machine. It can be readily appreciated that the assembly jigs and conveying devices of these two patents do not lend themselves to the handling of a so-called half pallet having one set of deck boards in place, for nailing a second set of deck boards to the same stringer beams to complete a double deck pallet. The stringer holding devices utilized in conjunction with the jigs of these patents would interfere with the handling and nailing of a half or partially completed pallet having one set of deck boards already nailed to stringers.
U.S. Pat. No. 3,755,871 discloses that partial or half pallets may be placed in the same basic nailing machine by hand, and U.S. Pat. No. 3,539,087 discloses side mounted conveyor chains to pull a jig holding stringers and deck boards through a nailing machine. However, there is no known prior art nailing apparatus or procedure which can accomplish the automatic processing of either single or double deck pallet components into and through the same nailing machine. It is with these shortcomings in mind that the pallet nailing apparatus and method disclosed herein have been developed.